1. Field of the Invention
The present invention relates to a hermetic compressor for use in, such as, a refrigerator and an air conditioner.
2. Description of the Prior Art
Recently, hermetic compressors of reduced size and with reduced vibration and noise have been largely demanded in refrigerators, air conditioners and the like irrespective of their types.
One of the typical conventional hermetic compressors is disclosed, such as, in Japanese Unexamined Patent Publication No. 4-171278, which will be briefly discussed with reference to FIGS. 9 and 10.
FIG. 9 shows a horizontal cross-sectional view of the conventional hermetic compressor with components in a sealed casing being illustrated in a top plan view, along with a schematic diagram of other components of the entire refrigeration system. FIG. 10 shows a partly-sectioned enlarged view of a portion A identified by a circle in FIG. 9. In FIG. 9, the hermetic compressor 1, along with a condenser 15, an evaporator 16 and an expansion valve 17, forms the refrigeration system 18 in which a refrigerant 12 is hermetically enclosed for-circulation therethrough. The hermetic compressor 1 includes the sealed casing 14 which accommodates therein a driving unit 19 in the form of an electric motor having a stator and a rotor, and a compressing unit 20 having a cylinder 24 and a piston 25 received in the cylinder 24. The driving unit 19, when energized, causes a reciprocating motion of the piston 25 in the cylinder 24 via a crankshaft and a connecting rod. The sealed casing 14 further accommodates therein an induction pipe 21, a discharge pipe 22, an induction muffler 23 and a discharge muffler 26. In FIG. 10, numeral 28 denotes a compression chamber in the cylinder 24, which communicates with the interior of the discharge muffler 26 via a discharge chamber 27 formed in a cylinder head and a communication passage 29 having a downstream end or an outlet 30 which is opened to the interior of the discharge muffler 26. The communication passage 29 is formed in a base block having the cylinder 24 therein.
Now, the operation of the conventional hermetic compressor 1 as structured above will be described hereinbelow.
When the driving unit 19 is energized, the rotor of the driving unit 19 starts to rotate so that the piston 25 starts a reciprocating motion via the crankshaft and the connecting rod. Accordingly, the refrigerant 12 circulated from the evaporator 16 and introduced into the sealed casing 14 via the induction pipe 21 is further sucked into the compression chamber 28 of the cylinder 24 via the induction muffler 23. The sucked refrigerant 12 is compressed in the compression chamber 28 during the compression stroke of the piston 25 so as to be introduced into the interior space of the discharge muffler 26 from the outlet 30 via the discharge chamber 27 and the communication passage 29. Thereafter, the compressed refrigerant 12 is conducted to the exterior of the sealed casing 14 via the discharge pipe 22. Specifically, the compressed refrigerant 12 introduced to the exterior of the sealed casing 14 is conducted to the condenser 15 to be condensed and then to the expansion valve 17 for immediate expansion and further to the evaporator 16 where the cooling action is performed.
As appreciated, since the refrigerant is sucked into the compression chamber 28 during a half rotation of the crankshaft and compressed during a subsequent half rotation of the crankshaft, the pressure pulsation of the refrigerant is inevitably generated, which causes vibration and noise at the hermetic compressor 1 and further may vibrate the condenser 15, leading to the generation of vibration and noise at the entire refrigeration system 18.
In order to suppress the generation of such vibration and noise, the pressure pulsation of the refrigerant should be reduced in the hermetic compressor. However, the conventional hermetic compressor as described above can not effectively reduce such pressure pulsation.